Get all the sources of your TCP sources, including the sources for
libraries.

run ATASYN from the directory in which it was installed:
ATASYN <tcp_src_directory> <compilation_spec_file_name>

A sample source code for TCP can be found here.
This is a modified version of
lwip
stack to suit the structure of ATASYN.
Compiling any TCP code would also require the source code of standard
libraries that need to be linked with TCP code. In the absence of that
ATASYN would complain so. It can be overcome by giving approximate cost of
running the library functions. The set of functions whose definitions or
running cost is required can be guessed by running ATASYN. And then given
to ATASYN as input when prompted.

For a wide range of possible average packet inter arrival times, the graph
gives the behaviour of the tcp code for different timeout times. A red
point signifies a possible synFlood scenario and a green one signifies a
possible safe scenario.